This invention relates to a refractory unit for a heat regenerator adapted to be used in a glass fusion furnace.
In a conventional glass fusion furnace, hot exhaust gas coming through a blow-off hole is introduced into a heat regenerator so as to heat refractory units. A majority of the heat transfer from the hot exhaust gas to the refractory units is of a radiant heat exchange type.
In contrast, the heat transfer from refractory units to cold air is mainly of a convection type. For such a reason, it is important that a refractory unit for a heat regenerator have a large specific surface. Also, turbulent air flow is better than laminar air flow.
A specific surface A (m.sup.2 /m.sup.3) can be expressed as follows: EQU A=S/V
where S is a total surface area (m.sup.2) of a gas-flow inner wall in a refractory unit and outer surfaces except two end surfaces and four corner surfaces and V is a total volume (m.sup.3) of both a gas flow passage and the refractory unit.
Japanese Utility Model Laying-Open No. 53-56452 and Patent Laying-Open No. 55-149139 disclose a cross type or hollow-prism type of refractory units.
Some conventional refractory units are made of an electro-cast refractory material.
FIG. 13 shows a conventional arrangement comprising a plurality of hollow-prism type refractory units 30. Each refractory unit 30 has a uniform thickness T over a full length thereof. The refractory units 30 are vertically stacked in such a manner that a plurality of octagonal flow passages 40 and square flow passages 60 are formed so as to extend in a vertical direction. Hot exhaust gas and cold air can flow through the flow passages 40, 60 one after the other for the heat exchange purpose.
However, such conventional refractory units lack an effective specific surface. For example, in each refractory units 30 of FIG. 13, assuming that the sectional area of the flow passage is 150 mm.times.150 mm, the wall thickness T is 40 mm and the height is 150 mm, the specific surface is only 24.1 m.sup.2 /m.sup.3. If the sectional area is 150 mm.times.150 mm, the wall thickness is 40 mm and the height is 140 mm, then the specific surface is the same number of 24.1 m.sup.2 /m.sup.3 as provided by a unit with a height of 150 mm.
As the inner and outer walls of each refractory unit are substantially flat, the gas is apt to flow through the flow passages 40, 60 as a laminar air flow and not a turbulent air flow. Thus, a convection type heat exchange cannot be easily carried out.
Moreover, the ridge or corner portions 50 of the refractory units 30 are flat and arranged in contact with each other. Thus, the refractory units 30 can slip by accident. In particular, if many refractory units 30 are stacked to a great height, they sometimes break loose due to an external force.